1. Technical Field
The present invention relates to magnetic field measurement apparatuses making use of light.
2. Related Art
Magnetic field measurement apparatuses making use of light are apparatuses that measure minute magnetic fields generated from biological objects, such as a magnetic field from the heart (magneto-cardiogram) and a magnetic field from the brain (magneto-encephalogram), and are expected to be applied in medical image diagnostic apparatuses and the like. An element in which a gas of alkali metal atom or the like is sealed is used in measuring a magnetic field. By irradiating pump light on the element mentioned above, energy of the atom in the element is excited in accordance with the magnetic field and a polarization plane of probe light having passed through the element is rotated due to a magneto-optic effect. A magnetic field measurement apparatus measures a rotational angle of the polarization plane as magnetic field information.
Researches to enhance the sensitivity of the magnetic field measurement apparatus have been carried out. A light pumping magnetometer that makes it possible to detect a magnetic field at a higher level of sensitivity by increasing the intensity of a detection signal is disclosed in JP-A-2009-236599.
However, the magnetometer disclosed in JPA-2009-236599 has a problem in that its sensitivity is lowered if there exists a magnetic field disturbance in a direction other than the direction of a magnetic field to be measured.